ShopBot off 1/4'' after cutting file

[wesday]

My prt96, after cutting a file, is nearly always a 1/4" short of 0,0 when it finishes. Some times a little more or a little less. Sometimes not at all. I have checked the table for square, new bit, greased gears etc.
I am cutting 1/2" mdf at 1.8" per sec. 3/16 spiral O bit, ramp is .45 (I think). It seems to "hit" sorta hard when ramping. This problem dosen't seem to happen when I am just drilling holes, only when actually cutting. The table seems to be rigid. Shopbot steel table.

Thanks for any input,
Wes

[wesday]

1/4" off on the x,y axis.

[gerald_d]

What are your typical:
- speed settings
- ramp settings
(sometimes they are incompatible - generally a ramp value around 0.6 times the speed value works okay)

What PC is driving your system:
-486?
-Pentium?
-Etc.
(we had an under-powered PC that was giving us jerky motion)

What SB software version have you installed?
(some of the software versions are understood to be problematical - I don't exactly know which, but have discovered that the latest is not always the greatest)

Have you sent a report to ShopBot service? They will give you better advice than here. Your problem is significant and not too trivial for the real SB service guys. This (http://www.shopbottools.com/req_techsup.htm) is how you should report it to ShopBot. Remember to send your problem.log file as well.

[wesday]

Speed Settings = 1.8 Cut & .45 (Ramp Too Slow??)
Software = v2.35
Computer = Pent. 200 W/ 64 megs ram

Thanks
Wes

[kerrazy]

what is the depth you are cutting in one shot.
It sounds like you are loosing steps.
Remeber a good rule of thumb is 1/2 the cutting diameter per pass at greater speeds of which I would say 1.8 is.

I would try a speed of 1.25 and a ramp of .75 and a cutting depth of 3/16th per pass.

This should reduce missed steps.

Dale
Also the 2.35 I believe has some hiccups so you may want to get the latest software and ensure you load the control box loader

[Ryan P]

I cut 1/2", 3/4" and 1" MDF in one pass with the same speeds you are cuting and lose no steps. I us a 3/8" spiral up cut. Your speeds should not be the problem.

[wesday]

I loaded the newer software. Seems to be doing ok now. I cut about 10 - 20 sheets a month at this feed rate and depth and have had no serious problems until lately.

Thanks,
Wes

[Grandpas@ix.netcom.com]

Dull bits will cause the same problem. Sometimes even a new bit cuts badly. That puts new stress on the motion and causes loss of stepper action.
Try a new bit and see what happens

[rgbrown@itexas.net]

Wes,

In addition to the above mentions, which are correct, have you greased your gear-rack recently? After your cuts and missed steps is your machine still square?

On my old - very old for a ShopBot, machine once it got a little out of square or it needed greasing, all kinds of interesting things happened until I got it ALL corrected. The cable machines were even more interesting....

Ron

Diplomacy is the art of saying 'Nice doggie' until you can find a rock. - Will Rogers